Programmed filter

ABSTRACT

A filter is provided for a smoking tobacco product, the filter having one or more channels which by-pass the main body of filtering material such that a portion of the smoke is caused to flow through the channel and a relatively short portion of the filter in the earlier puffs, while essentially all of the smoke flows through the main body of the filtering material in later puffs. Through the gradual change from a portion of the smoke flowing through the channel to all of the smoke flowing through the main filter body, the filter accomplishes a nearly uniform per puff delivery of total particulate matter, through a relatively steady increase in filter efficiency.

United States Patent [191 Hammersmith et al.

[4 Oct. 7, 1975 PROGRAMMED FILTER [73] Assignee: Brown and WilliamsonTobacco Corporation, Louisville, Ky.

[22] Filed: July 5, 1974 [21] Appl.. No.: 486,021

Related US. Application Data [63] Continuation of Ser. No. 336,277, Feb.27, 1973,

[58] Field of Search l31/10.'5,10.3,l0 A, 10.7, 131/201, 261 B, 15 B,10.9, 210,10 R

[56] References Cited UNITED STATES PATENTS- 2,958,328 11/1960Bartolomeo 3,270,750 9/1966 Campbell 13 l/l 0.3 3,428,050

2/1969 Kandel 13l/l0.3

- 3,596,664 8/1971 Pinkham l3l/l0.5 3,651,819 3/1972 Beard 131/261 B3,752,165 8/1973 Harllee et al. 13l/10.5 3,768,489 lO/l973 Kiefer et al.131/261 B Primary Examiner-Melvin D. Rein Assistant Examiner-John F.Pitrelli Attorney, Agent, or FirmVance A. Smith [5 7 ABSTRACT A filteris provided for a smoking tobacco product, the filter having one or morechannels which by-pass the main body of filtering material such that aportion of the smoke is caused to flow through the channel and arelatively short portion of the filter in the earlier puffs, whileessentially all of the smoke flows through the main body of thefiltering material in later puffs. Through the gradual change from aportion of the smoke flowing through the channel to all of the smokeflowing through the main filter body, the filter accomplishes a nearlyuniform per puff delivery of total particulate matter, through arelatively steady increase in filter efficiency.

12 Claims, 11 Drawing Figures U.S. Patent Oct. 7,1975 Shezt 1 S533,91%,28

PROGRAMME!) FILTER RELATED APPLICATIONS This is a continuation of US.Ser. No. 336,277 filed Feb. 27, 1973, now abandoned.

BACKGROUND OF THE INVENTION In recent years there has been a tendency inthe'tobacco industry to use filtering materials for smoking tobaccoproducts, particularly cigarettes, having greater and greaterefficiencies. Efficiencies, in this sense, are defined as the amount oftotal particulate matter removed from the smoke created by the burningtobacco before it reaches the smoker.

While the increased efficiency is frequently desirable, the first fewpuffs of a smoking tobacco product employing such a high efficiencyfilter generally have no taste or impact for the smoker. For these firstfew puffs, not only does the high efficiency filter act to removeasignificant portion of the total particulate matter, but the effect ofthe entire tobacco column is added to the effect of the filter. Thecombination is such as to remove almost all of the total particulatematter so that the smoker receives no satisfaction from these first fewpuffs.

While not directed to the same problem, the provision of channels in afilter for a smoking tobacco product is described in US. Pat. No.3,270,750Campbell. Various locations and configurations for the channelare provided, the channel running the entire length of the filtersection. It will be noted that with each of these locations andconfigurations, however, the channel is closed before the cigarette isused through application of digital pressure. The filtering element isspecifically formed in such a manner as to be crushable.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the presentinvention one or more channels are formed on or within a filteringelement for a smoking tobacco product, such as a cigarette, where thefiltering element is formed in such a manner or provided with protectionso as to prevent crushing and leave the channel member generally openthroughout smoking of the product. While the beginning of the channel iscontiguous with the tobacco section of the smoking product, the channelterminates short of the mouthpiece end. At the termination of thechannel, a small orifice leading to the filter material is provided.

The filtering element is so formed that it is generally resistant tocrushing, so that the channel may remain open during the entire courseof smoking the smoking product.

In the initial stages of smoking, because of the sizing of the channeland hole taken together with the efficiency of the filtering element, atleast some of the smoke generated by burning the tobacco product passesthrough the channel and orifice and then through a shortened portion ofthe filtering element. The walls of the channel, except for the orifice,are essentially impervious to the smoke, so that there is no filtrationthrough these walls. During the course of smoking, the area of thefiltration element adjacent the orifice gradually becomes plugged due tothe accumulation of solid material. As the plugging continues, there isincreased resistance to smoke passing through this shortened portion ofthe filter so that, gradually,

all, or essentially all, of the smoke generated by the burning tobaccoproduct will pass directly through the main filter section. In thismanner, there is a general leveling of delivery of total particulatematter.

Additionally, though a high efficiency filter is employed, because ofthe shortened path of the first few puffs through the filtering element,the puffs provide a generally full taste. As is known, in general, thefirst few puffs of a cigarette have a generally low total particulatematter content, in any event. In large part, this is due to thefiltration effect of the tobacco column so that maximum filtration bythe filtering element is not required, in any event.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is a perspective view of a preferred programmed filter of thepresent invention having a single channel on the periphery;

FIG. 2 is a plan view of the filtering element of FIG. 1 incorporatedinto a smoking product;

FIG. 3 is a plan view of a filtering element according to the presentinvention having two channels, where the channels are of unequal length;

FIG. 4 is a plan view of a filtering element according to the presentinvention, incorporated in a smoking tobacco product, where the channelsformed in the filtering element are of equal length;

FIG. 5 is a plan view of a filtering element according to the presentinvention where the channel formed in the periphery of the filteringelement is tapered;

FIG. 6 is a plan view of a filtering element according to the presentinvention incorporated in a smoking product, where the channel isexternal to the filtering element; I

FIG. 7 is a plan view of a filtering element according to the presentinvention incorporated in a smoking product where the channel is formedwithin the body of the filtering element, rather than along the periph-FIG. 8 is a sectional view along the line 88 of FIG.

FIG. 9 is a plot showing the milligrams of total particulate matterdelivered on a per puff basis for programmed and unprogrammed filters;

FIG. 10 is a plot showing the efficiency, on a per puff basis, ofprogrammed and unprogrammed cigarette filters; and

FIG. 11 is a plot of total particulate matter delivery, on a per puffbasis, illustrating the effect of varying orifice size.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the accompanyingdrawings, a filtering element 1 of the present invention is illustratedin FIG. 1. The filtering element includes a high efficiency filteringmaterial 2 encased in a stiff plastic casing 3 within which is formed achannel or groove 4. An orifice 5 is formed at the terminus of thechannel or groove. In FIG. 2 the filtering element 1 illustrated in FIG.1 is shown incorporated in a cigarette including a tobacco section 6 anda wrapper 7 which encases both the tobacco section 6 and the filteringelement 1. It will be noted in FIG. 2 that the open end 8 of channel 4is adjacent the tobacco section while no groove appears at themouthpiece end 9 of the smoking tobacco product.

In FIG. 3 a filtering element 11 is incorporated in a smoking tobaccoproduct including a tobacco section 16, both the filtering element andthe tobacco section being encased in a wrapper 17. The filtering element1 1 illustrated in FIG. 3 has a longer channel 12 with its open end 13adjacent the tobacco section 16 and an orifice 14 at the end of thechannel. A shorter channel 18 is also formed in the filtering elementwith the open end 19 of this channel also adjacent the tobacco sectionand an orifice 20 formed at the closed end of the channel. Again, thechannels terminate short of the mouthpiece end of the cigarette.

In FIG. 4 a filtering element 21 is illustrated, similar to filteringelement 11. The filtering element is incorporated with a tobacco section26 by wrapper 27. The two channels 22 and 22' of filtering element 21each have the open portions 23 and 23 of the channels adjacent thetobacco section while the closed portions of the channels are formedwith orifices 24, 24.

In FIG. 5, filtering element 31 is again incorporated with a tobaccosection 36, the two portions being enrobed in wrapper 37. Filteringelement 31 includes a single channel 32, the channel differing from thechannels described in the previous figures by tapering, the largestportion of the channel being the open end 33 adjacent tobacco section36. The channel gradually tapers to orifice 34 formed at the closed endof the channel. Again, the channel terminates short of the mouthpieceend of the cigarette.

In FIG. 6, a filtering element 41 is shown including high efficiencyfiltration material 42. The filtration material is adjacent a tobaccosection 46 and the filtration material 42 and tobacco section 46 areheld together by member 47 which may be 'a portion of a cigaretteholder. Formed within member 47 is a channel 43 which connects theportion of the tobacco section closest the filtering elernent 42 to thefiltering element 42 near, but not at, themouthpiece end 44 of thesmoking product.

In FIG. 7 a filtering element 51 is illustrated in combination with atobacco section 56, the two sections being enrobed in a common wrapper57. A channel 52 is formed within the high efficiency filtrationmaterial 53, rather than on the periphery of this material. The open endof the channel 54 is again adjacent the tobacco section 56 and anorifice 55 is formed in the closed end of the channel.

It will be appreciated that the filtering elements shown in each of thefigures are not necessarily drawn to scale, but rather illustratevarious embodiments possible within the concept of the presentinvention. In general, the channels are shown as having a lengthapproximately 80 percent of the overall length of the filtering element.Generally, the channel or channels should have lengths of about 50 to 85percent of the length of the filtering element. In each case, thechannels and orifice sizes are generally shown larger than they wouldactually be formed in order to render the illustration clearer. Theparameters for the various lengths and sizes will be given in moredetail below.

In designing a workable filter of the type described herein, severalfactors are of particular importance. The overall efficiency of thistype of filter is determined, to a great degree, by the particular typeof filter element selected for the main body of the filter. As such, thenormally important parameters including the type of tow, the weight ofthe rod, the circumference, and the fiber distribution are important.

With the programmed filter of the present invention, the additionalfactors of importance are the size of the orifice at the end of thechannel, the non-porous walls lining the channel, and the initialrelationship between the resistance of the smoke flow path through thechannel and orifice compared with the initial resistance through themain body of the filtering element. Also of importance are the shape andplacement of the orifice, the compression of the tow, the dimensions ofthe groove, and the orientation of the fibers within the main filteringelement, particularly that part of it adjacent the orifice.

The initial resistivity ratio of the programmed filter is defined as thepressure drop of the main filter section divided by the pressure drop ofthe shortened flow path which includes the groove, orifice, and shortsection of the filter element. These values are' obtained,independently, with a 17.5 cc./sec. air flow. The percentages of theinitial smoke puff which flow through the groove and orifice, ascompared with the flow through the main filter section, at varyingresistivity ratios are shown below in Table I:

TABLE 1 INITIAL RESISTIVITY RATIO COMPARED WITH SMOKE FLOW Percent ofPuff Volume Through Ratio Groove Orifice Main Filter Element In general,regardless of the main filter element employed, the programmed filterwith the greatest resistivity ratio will give the lowest initialefficiency and the greatest rate of efficiency increase in later puffs.The initial resistivity ratios desired for the programmed filters of thepresent invention are from 0.5 to 5.0, preferably 1.0 to 3.0. When theinitial resistivity ratio is below 0.5, the'programming effect is notrealized. Above a resistivity ratio of 5.0, there are problems of theorifice being too large to be effectively blocked during the initialpuffs, or of blocks which are broken in the later puffs. In thepreferred range of I to 3, the initial resistance through the grooveorifice in short filter section is obviously equal to or less than theresistance through the main filtering element. Consequently, during thefirst puff from 50 to 75 percent of the smoke passes through the lowerefficiency groove orifice. As this path becomes gradually blocked, moreand more of the smoke passes through the main filter section. Ingeneral, by the fourth or fifth puff the resistance through the grooveorifice is greater than the resistance through the main filter elementso that the largest part of the smoke passes through the main filterelement. Normally, by the last puff, the orifice is almost totallyblocked and essentially all of the smoke passes through the main filterelement.

The effect of this programming can be seen in FIGS. 9 and 10. In FIG. 9,the total particulate matter delivery per puff is shown both for astandard cellulose acetate filter and for a programmed filter of thepresent invention. It can be seen that the milligrams delivered per puffis essentially the same for the first as for ninth puff with theprogrammed filter, while with-the normal cellulose acetate filter, thedelivery of total particulate matter per puff has more than doubledwithin these puff ranges. The reason for this leveling of tar deliveryper puff is seen in FIG. where the efficiency of the filter for eachpuff is illustrated. Here, the efficiency of the standard celluloseacetate filter is changed verylittle between the first and ninth puffs,while the efficiency of the programmed filter increases fromapproximately 40 percent to 60 percent during this same period ofsmoking.

The optimum sizeof the orifice formed at the end of the channel, when asingle channel and orifice are used,

is from about 12 to 30 Birmingham or Stubs gauge or about 0.07 to 6.0square millimeters in cross-sectional area. Preferably, the orifice sizefor such a filtering element is from 12 to 21 Birmingham or Stubs gaugeor about 0.5 to 3.5 square millimeters in cross-sectional area. The sizeof the channel leading to the hole should be from about 1 to 3millimeters diameter, and, generally, slightly greater than the orifice.While the channel size is expressed as a diameter, it is thecross-sectional area of the channel, and not its configuration or diameter which are the critical factors.

I The area of the channel should not be too great or there is a dangerthat the area of the main body of the filtration'material will be toosmall, the channel representing a portion of the main filtration volumebeing removed. The length of the channel is not critical and it isselected such that the relative resistance between the main body of thefiltration material and the chan nel, orifice and short section of thefiltration material are within the ranges recited above.

Some impaction is necessary to provide a buildup of the particulatematerial in the portion of the filtration material adjacent the orificeat the end of the channel. The proper velocity for this is providedthrough sizing of the channel as indicated above.

When more than one channel and orifice are employed, as illustrated, forexample, in FIGS. 3 and 4, the total area of the plurality of orificesshould be slightly larger than the area of a single orifice toaccomplish the same result. Because the buildup of particulate materialaround the orifice in the filtration material generallyoccupies anessentially hemispherical configuation, more particulate matter isrequired to block one orifice than a plurality of orifices having thesame area. Thus, the size of the plurality of orifices is increased,relative to the single orifice, so that essentially the same amount ofparticulate matter is required to block the plurality of orifices aswould be required for a single orifice and the same type of programmingis obtained. With a plurality of orifices as illustrated in FIG. 3, forexample, where the channels are of unequal length, one channel, e.g.,channel 12, may be the channel through which smoke flows during thefirst few puffs of the cigarette, after which the smoke flow may shiftto a second channel, as channel 18, and finally through the main body ofthe filtration material. Of course, thoughonly two channels areillustrated in FIG. 3, a different number might be employed.

The effect of varying orifice size, within the stated range, isillustrated in FIG. 1 1. With the same filter element material employedin each case, the total particulate matter delivery in milligrams perpuff is plotted against puff numbers from 1 thru 9. It can be seen thatas the orifice size becomes smaller, there is a greater leveling ofparticulate matter delivery, per puff, as other factors are unchanged.Again, the leveling of particulate matter deliveries compared to acontrol is easily seen.

If desired, the single channel of most of the illustrated embodiments,or one or more of the channels illustrated in FIGS. 3 and 4, may befilled or partially filled with a material to accomplish a particularresult. For example, a flavorant might be placed in the channel toflavor the earlier puffs of the smoke. When such a material is includedin the channel, it should be of such a type and such an amount that theprogramming effect of the filter is not lost.

The main filtration element, e.g., 2 in FIG. 1, may be formed of variousfilter materials. For example, it may be formed of paper or celluloseacetate. It is, in general, selected for its filtration efficiency andwith a filtering element of the present invention, the filtrationefficiency for particulate matter should be at least about 50 percent.

As illustrated in FIG. 1, the main body of filtration material issurrounded by a plastic sleeve where the channel is formed in thissleeve and the orifice at the end of the channel is formed through thesleeve. The function of the plastic sleeve is twofold:

1. It prevents crushing of the filter which would destroy the channel.

2. It renders the walls of the channel impervious, so that filtrationdoes not take place through these walls. The plastic sleeve is not acritical feature of the present invention, so long as its two functionsare provided. Thus, for example, after formation of the channel in thefiltration material, the periphery of the filtration material may becoated so as to provide the necessary seal and increase the mechanicalstrength. Depending upon the particular filtration material employed,heat sealin g may also be used. H

The effects of the various parameters mentioned above on operation ofthe programmed filter are illustrated in Table 2. The various parametersare set forth and the effect of an increase in any of these parametersis given with regard to the initial filter pressure drop, initial filterefficiency, amount of initial flow through the channel and orifice,final filter .pressure drop, and final filter efficiency. An increase inany of these measured effects is shown as a a decrease as a and nochange with a 0.

In order that those skilled in the art may be better enabled to practicethe present invention, the following examples are given. These examplesshould be considered as illustrative, and not as limiting in any way thefull scope of the present invention as covered in the appended claims.

EXAMPLES l 3 In these examples the filter element was formed ofcellulose acetate filters having a denier of 1.6 per fiber and 24,000denier per filter and having an injected secondary crimp. Three filterswere formed with this material having, respectively, orifice sizes ofl9, l7 and 15 Stubs gauge or diametersof 1.1, 1.5 and 1.8 mm.,respectively. The total particulate matter deliveries in milligrams percigarette, initial pressure drops in inches of water gauge, initialresistance ratios, and filter efficiencies are shown in Table 3. It canthus be seen that with each of these filters there was a significantincrease in the filter efficiency from section is smoked, due toincreasing flow resistance through said channel filter means, wherebythe total particulate matter per puff delivered to the EXAMPLE 4 Ysmoker remains essentially constant during smok- In this example thecellulose acetate filter element 5 i f h tobacco section, id h l means ihad denier P fiber l fi i total denier- The eluding at least one channelhaving essentially orifice diameter was 1.8 millimeters, a Stubs gaugeof Smoke impervious walls, an Open upstream end The total particulatematter delivery was ommunicating the tobacco ection and a ingrams Pcigarette and the 'hmal P e h p gle orifice at the downstream end ofsaid channel Inches of Water gauge was The lhlhal resletahee 10 adjacentsaid filtration material at a position short ratio was The elgerette hefhelehcyi of the mouthpiece end of said main filtration eleoverall of50 percent including an initial efficiency of ment the area of theOrifice is from about 007 to 34 percent and a final efficiency of 65percent. 2

EXAMPLE 5 2. The filtering element of claim 1 wherein said channel meansis a single channel formed in said main filtra In this example acellulose acetate filter element hav- 2 t'b d 1d 44 000 element mg demerper er d tota emer o was 3. The filtering element of claim 2 whereinsaid chanemployed. The orifice diameter was 1.8 mm., a Stubs nel isformed on the periphery of said main filtration gauge of 15. The totalparticulate matter delivery for element the cigarettes was 17.6milligrams. The initial pressure 4. The filtering element of claim 2wherein said chandrop was 2.2 inches water gauge and the initialresistivnel is formed axially within said main filtration element. ityratio was 1.4. The cigarette showed an overall efi'i- 5 Th f. l ciencyof 31 percent including an initial efficiency of lterfng e emem of clamwherem the area 16 percent and a final efficiency of 47 percent. of theonfice from to While the invention has described with particular ref-The fihenhg element of elalm 2 where"! Sald Chanerence to the drawingsand particular examples, it nel l5 tapered 7 should not be considered asso limiting, but only as lim- 7. The filtering element of claim 1wherein said chanited by the appended claims. nel means is a pluralityof channels, each having an TABLE 2 Parameter Initial Filter InitialFilter Initial Flow Thru Final Filter Final Filter Increased PressureDrop Efficiency Channel and Orifice Pressure Drop Efficiency OrificeSize Channel Area 0 Efficiency of Filter Element Distance of OrificeFrom Suction End of Filter 0 O TABLE 3 Filter Efficiency Percent HoleDiameter Initial Pressure Drop initial Resistance Stubs Gauge lnchesWater Gauge Ratio Overall Initial Final We claim: open end communicatingwith said tobacco section and 1. A filtering element for a smokingproduct comprisan orifice adjacent the filtration material.

ing

a. a main filtration element, containing filtration material and havinga mouthpiece end, for disposition in substantial alignment with atobacco section and b. channel filter means of an initial flowresistance equal to or lower than said main filtration element forcausing predetermined proportion of the smoke from the tobacco sectionto initially by-pass a part of the filtration material and move throughsaid channel filter means and further causing a predetermined increasingproportion of the smoke to 8. The filtering element of claim 7 whereintwo channels are formed.

9. The filtering element of claim 7 wherein each of said channels is ofthe same length.

10. The filtering element of claim 7 wherein the channels are ofdifferent lengths.

11. The filtering element of claim 10 wherein the length of one channelis greater than the length of the other channel.

12. The filtering element of claim 1 wherein the channel filter meanslies outside the main filtration elepass through said filtrationmaterial as the tobacco 5 ment-

1. A filtering element for a smoking product comprising a. a mainfiltration element, containing filtration material and having amouthpiece end, for disposition in substantial alignment with a tobaccosection and b. channel filter means of an initial flow resistance equalto or lower than said main filtration element for causing predeterminedproportion of the smoke from the tobacco section to initially by-pass apart of the filtration material and move through said channel filtermeans and further causing a predetermined increasing proportion of thesmoke to pass through said filtration material as the tobacco section issmoked, due to increasing flow resistance through said channel filtermeans, whereby the total particulate matter per puff delivered to thesmoker remains essentially constant during smoking of the tobaccosection, said channel means including at least one channel havingessentially smoke impervious walls, an open upstream end communicatingwith the tobacco section, and a single orifice at the downstream end ofsaid channel adjacent said filtration material at a position short ofthe mouthpiece end of said main filtration element, the area of theorifice is from about 0.07 to 6.0mm2.
 2. The filtering element of claim1 wherein said channel means is a single channel formed in said mainfiltration element.
 3. The filtering element of claim 2 wherein saidchannel is formed on the periphery of said main filtration element. 4.The filtering element of claim 2 wherein said channel is formed axiallywithin said main filtration element.
 5. The filtering element of claim 2wherein the area of the orifice is from 0.5 to 3.5mm2.
 6. The filteringelement of claim 2 wherein said channel is tapered.
 7. The filteringelement of claim 1 wherein said channel means is a plurality ofchannels, each having an open end communicating with said tobaccosection and an orifice adjacent the filtration material.
 8. Thefiltering element of claim 7 wherein two channels are formed.
 9. Thefiltering element of claim 7 wherein each of said channels is of thesame length.
 10. The filtering element of claim 7 wherein the channelsare of different lengths.
 11. The filtering element of claim 10 whereinthe length of one channel is greater than the length of the otherchannel.
 12. The filtering element of claim 1 wherein the channel filtermeans lies outside the main filtration element.